3 – Lecture Chemical bonding and Molecular Structure Azamat Amzebek
Topics Covered Ionic Bonds and Compounds Covalent Bonds Lewis Structures Types of Covalent Bonding Geometry and Polarity of Covalent Molecules Orbital Hybridization Sigma and Pi Bonds
Chemical bond The atoms in molecules held together by strong attractive forces called chemical bonds Formed by interaction of valence electrons of the combining atoms In the formation chemical bonds atoms bond according to the octet rule
Ionic bond Two atoms with large difference in electronegativity reactivity, there is complete electron transfer High electronegativity == anion Low electronegativity == cation
Ionic bond These two ions are held together by electrostatic forces This force of attraction between the charged ions is called an ionic bond
Nomenclature 1. 2. 3.
Nomenclature 4. 5.
Nomenclature 6.
Ionic bond High melting and boiling point – strong electrostatic force Conduct electricity in liquid and aqueous states
Covalent Bonds Forms when two elements have similar electronegativities They achieve a noble gas electron configuration by sharing electrons in what is known as a covalent bond Sometimes need more than one electron to form octet
Covalent bond Bonds length is the average distance between the two nuclei of the atoms involved Bond energy is the energy required to separate two bonded atoms
Bonds Primary bonding – covalent and ionic Secondary – hydrogen and Van der Vaals
Lewis Structures Valence electrons of a covalent bond – bonding electrons Valence electrons not involved in the covalent bond – lone electron pairs(nonbonding) Lewis structure – convenient representation of bonding and nonbonding electrons in a molecule
Lewis Structures More than one Lewis structure for a molecule – resonance
Formal Charge
Formal Charge
Resonance structures
Types of covalent bonds Polar covalent bonds – occurs between atoms with small difference in electronegativity Nonpolar covalent bond occurs between atoms that have the same electronegativites Coordinate Covalent Bond – the shared electron pair comes from the lone pair of one of the atoms in the molecules
Lewis acid and base Lewis base NH 3 – donor of pair if electrons Lewis acid BF 3 – acceptor of pair of electrons
Geometry and polarity The Valence Shell Electron - Pair Repulsion Theory
Geometry and Polarity
Hybridization sp – hybridization
Hybridization
Sigma and Pi bonds
Metallic bond
Summary
Summary
Summary
Summary
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